Nuclear pulse counting experiments, of which X-ray fluorescence analysis is exemplary, in principle, sorts radiation counts according to magnitude and tabulates the counts in each magnitude or energy characterization. The count data on a statistical basis is used to calculate, for example, sample/matrix concentrations.
Generally typical systems of the kind involving nuclear pulse count analysis employ the combination of a count detector, stepwise amplification of the counts, and count sorting, tabulation, and calculation functions. In typical X-ray analysis, for example, most commonly two, and possibly up to four, energy characterizations are employed to sort the counts. Since the backscatter and fluorescence peaks are mathematically related, preferred modes identify the more prominent backscatter peak, and from that data compute the position of the fluorescence peak. The mode of identifying the backscatter peak is most often by peak stabilization techniques accomplished through gain factoring methods. Thus normally, it will be observed that typical prior art systems rely on some form of an amplification gain stabilizer.
Disadvantages of such systems are unsuitability of the technique unless threshold count densities are established. Thus since gain stabilization is based on the principle of monitoring narrow "energy" windows on each side of the stabilized peak center line, insufficient count density necessary to produce a statistically reliable and balanced numerical count in each monitored area, develops conditions whereby the center line may meander. In such cases, the X-ray analytical technique is generally unsuitable, or may force the selection of a radiation source that is not optimum for the experiment.
Typical precision achieved by the prior methods may be expressed generally as about .+-.3% relative. Improvements over this number may be achieved by utilizing highly sophisticated detector forms, as exemplified by lithium/germanium detectors, with required liquid nitrogen cooling systems. However, the advantage of using the latter optimum detector form is frequently offset by the extreme damage prone and fragile nature of the detector. Such are thus oftentimes judged unsuitable for industrial applications, and substitution with less precise but otherwise more suitable scintillation detectors and/or proportional counters is usually preferred.